Sp. Char. Adult. Upper parts rich blackish-brown, approaching black on the back; scapulars and middle wing-coverts edged and barred beneath the surface with dull white, and tinged along edges with ochraceous. Wings generally of a paler shade than the back; secondaries fading into nearly white at tips, and, with the greater coverts, obscurely barred with darker; primaries nearly black, tips edged with pale brown, this passing into whitish. Rump uniform blackish-brown, feathers obscurely bordered with rusty. Upper tail-coverts ochraceous-white, nearly pure terminally, and with about two distinct transverse bars of deep rufous. Tail rich uniform lateritious-rufous, passing narrowly into white at the tip, and about an inch (or less) from the end crossed by a narrow band of black. Head and neck with the feathers medially blackish-brown, their edges rusty-rufous, causing a streaked appearance; the rufous prevailing on the sides of the occiput, the ear-coverts, and neck. The blackish almost uniform on the forehead and on the cheeks, over which it forms a broad “mustache”; lores and sides of frontlet whitish. Throat white, with broad stripes of pure slaty-brown; lower parts in general ochraceous-white; tibiæ and lower tail-coverts immaculate; across the abdomen and flanks (immediately in front of the tibiæ) is a broad interrupted belt of longitudinal black blotches, those on the abdomen tear-shaped, on the flanks larger and more irregular, throwing off bars toward the edge of the feathers; whole pectoral area variegated only with a few shaft-streaks of black (these growing broader laterally), and sometimes washed with rusty. Lining of the wing ochraceous-white, with sparse diamond-shaped spots of pale rufous, and shaft-streaks of darker; under surface of primaries white anterior to their emargination, beyond which they gradually deepen into black; the innermost ones are finely mottled with slaty, and with imperfect transverse bars of the same.
Male. Wing, 13.50–16.50; tail, 8.50–10.00; culmen, .95–1.08; tarsus, 1.40–3.20; middle toe, 1.60–1.70. Weight, 2½–3 lbs.
Female. Wing, 15.25–17.75; tail, 9.50–10.50; culmen, 1.00–1.15; tarsus, 3.15–3.40; middle toe, 1.70–1.80. Weight, 3–4 lbs.
Young (28,154, Philadelphia; J. Krider). Above similar to the adult, but lacking entirely any rufous tinge, the scapulars and wing-coverts more variegated with whitish. Tail light grayish-brown (very much lighter than the rump), tinged, especially basally, with rufous, narrowly tipped with white, and crossed with nine or ten narrow, curved bands of black; upper tail-coverts white, with broad bars of black. Head as in the adult, but the rufous wanting, leaving the streaks black and white; forehead more broadly white; chin and throat wholly white, the latter with a collar of dusky streaks across the lower part; whole pectoral region entirely immaculate, pure white; abdominal band as in the adult; tibiæ somewhat tinged with ochraceous, unvariegated.
Hab. Eastern North America; not in West Indies, nor west of the Missouri.
Localities: (?) Bahamas (Bryant, Pr. Bost. Soc. 1867, 64).
LIST OF SPECIMENS EXAMINED.
National Museum, 9; Philadelphia Academy, 13; Boston Society, 8; Museum, Cambridge, 15; Cab. G. N. Lawrence, 3; Coll. R. Ridgway, 2. Total, 50.
The true Buteo borealis, as restricted, may always be distinguished from the var. calurus, its western representative, by its having the posterior lower parts (tibiæ and lower tail-coverts) entirely free from transverse bars, and by lacking indications of transverse bars on the tail, anterior to the conspicuous subterminal one. It differs from the var. costaricensis, in having the head and neck conspicuously striped with rufous, and the throat thickly striped with black, almost obliterating the white; in the conspicuous abdominal belt of large black spots, and in having the tibiæ lighter ochraceous than the breast; from the var. lucasanus and var. krideri, it is distinguished by having the black tail-band, more spotted under parts, and in the upper tail-coverts being white, banded with rufous, instead of plain white, or deep rufous, uniform with the tail.